Tehran today gave a guarded welcome to a newly-announced US plan to invite Iran, Syria and others to discuss ways to stablise Iraq.

"We are reviewing the proposal," Ali Larijani, the head of Iran's supreme national security council was quoted as saying by a state TV website.

"We support solving problems of Iraq by all means and we will attend the conference if it is expedient," he said. "We believe Iraq's security is related to all its neighbouring countries, and they have to help settle the situation."

Downing Street also gave its support to the plans today, although the prime minister's spokesman warned that any success would depend on Iran and Syria, "whether they engage properly and whether we see a constructive attitude".

The announcement last night by the US secretary of state, Condoleezza Rice, in testimony to the Senate appropriations committee, reverses one of the central parts of the Bush administration's Middle East strategy.

The proposed meeting follows growing pressure on the US government to agree to talks with Tehran and Damascus, something recommended late last year by the Iraq Study Group.

Ms Rice said representatives from Iran and Syria would be invited to a "neighbours meeting" to discuss efforts to stabilise Iraq.

"I am pleased to announce that we are also supporting the Iraqis in a new diplomatic offensive: to build greater support, both within the region and beyond, for peace and prosperity in Iraq," she said.

The plan is for an initial gathering in March at a sub-ministerial level, followed by a full ministerial meeting, possibly in early April.

According to Iraq's foreign minister, Hoshiar Zebari, the meeting will include Iraq; its six neighbours; the five permanent members of the UN security council - the US, Britain, Russia, China and France; members of the Arab League; and the Organisation of the Islamic Conference.

Mr Larijani indicated today - somewhat cryptically - that the US presence at the meeting was not a problem for Iran. Asked by reporters if Iran was running a risk by attending the conference alongside the Americans, he replied: "One should not commit suicide because one is afraid of death."

Syria's foreign ministry has already confirmed that the country will be represented at the first meeting by Ahmed Arnous, an aide to the foreign minister.

Downing Street welcomed the planned talks today, but said it wanted to see "results on the ground".

"The Americans have always said they would take part in the contact group, so that is not new," the prime minister's spokesman said.

"In terms of Iran and Syria, the issue is not contact, the issue is what their response is and whether they engage properly and whether we see a constructive attitude.

"Meeting is good but results have to flow from meetings. We welcome contact, but equally what we want to see is hard, concrete results - that's on the ground in Iraq, that's on the ground in Lebanon, that's on the ground in terms of influence used in Palestine as well.

"Those are the results we are looking for."

According to US officials, the meetings will be limited to covering questions of Iraqi security. Topics such as Iran's banned nuclear programme or Syrian involvement in Lebanon remain off-limits.

"This is one where the agenda is being set up by the government of Iraq," the White House press secretary, Tony Snow, told reporters. He also indicated there would be no bilateral contact between the US and Iran.

The prospect of US and Iranian diplomats sharing a negotiating table in Baghdad represents an apparent U-turn on Mr Bush's strategy towards the Middle East. It follows increasing criticism even from those foreign policy experts who support the Bush administration policies on Iraq, such as James Baker and Henry Kissinger, who had been calling on the administration to end its diplomatic isolation of Iran. The outgoing ambassador to Baghdad, Zalmay Khalilzad, also favoured direct talks with Tehran§.

The limited diplomatic engagement follows several weeks of political manoeuvring between the White House and Congress, and a rhetorical offensive from Washington against Syria and Iran.

In recent weeks, US officials have accused Iranian agents of supplying militants inside Iraq with materials for roadside bombs that have taken a heavy toll on US forces, and of funnelling support to Hizbullah militants in Lebanon. They have also accused Syria of allowing insurgents and arms to cross its borders into Iraq.